1. Related Field
The present invention relates to a paper making machine for producing tissue paper. The invention also relates to a method of producing tissue paper and to an extended nip roll which is suitable for use in the inventive method.
2. Description of Related Art
A paper making machine for the production of tissue paper is known from U.S. Pat. No. 5,393,384. The paper machine shown therein has a belt impermeable to water which runs in a loop through an extended press nip formed by a shoe press and a counter roll. A press felt is conveyed through the press nip. In one embodiment, a shoe press has been placed such that the press shoe is capable of acting on the tissue drying cylinder. It is stated that the drying effect of the shoe press generates a considerably higher degree of drying than a corresponding roll press and that this, in the conjunction with a nonabsorbent belt which avoids remoistening of the web results in considerably increased drying capacities of a press unit.
Another paper making machine for soft paper such as tissue is disclosed in U.S. Pat. No. 6,547,924. The paper making machine shown in that patent also uses a substantially impermeable belt but this belt is a texturing belt which has a web-contacting surface defining a multitude of regularly distributed depressions and surface portions located between the depressions. The belt is used for the purpose of texturing a relief pattern in a fibrous web in order to increase its bulk. The substantially impermeable belt runs in a loop through a press with a shoe press roll and a counter roll and around a transfer roll that forms a transfer nip with a Yankee dryer.
Yet another paper making machine is shown in U.S. Pat. No. 7,811,418. The paper making machine shown in that patent uses a transfer belt that may have depressions and a permeable structuring fabric which is arranged to transfer the wet paper web to a drying cylinder. In embodiments described in that document, a shoe press is used in which the transfer belt passes through a press nip between a shoe press roll and a counter roll.
The above mentioned patents include a large number of components. It is desirable to reduce the number of components used in the machine.
U.S. Pat. No. 4,144,124 discloses a machine for manufacturing paper such a tissue paper. The machine disclosed in that patent comprises a twin-wire former and a press nip between an inner and an outer press roll. The upper or outer press roll is a suction roll which, together with a Yankee cylinder forms a second nip. An endless fabric such as a wire suitable for pattern embossing is may be used and is said to produce impressions in the paper at the press nips. This machine can use uses fewer rolls in the press section since the suction roll is used two nips, one nip with the so called “inner roll” and one nip with the Yankee cylinder.
It is an object of the present invention to provide a paper making machine for tissue paper which has a simple design and few parts and which is capable of producing a tissue paper web that has a high bulk. These and other objects are achieved by means of the present invention as will be explained.